The function of these kinds of rear vision mirrors are obvious in that they assist advising the driver the condition or situation of the happenings that are taking place at the back of the driver.
Nonetheless, in order to be placed in the optimum position to reflect the happenings that are taking place towards the rear and the side of the back section of the motor vehicle, such mirrors are often placed in locations that block out partial side view and some forward view of the driver.
Hence, though the rear vision mirror provides information as to the happenings of the rear of the vehicle, at certain moments in time if required, they do potentially restrict vision in certain side and forward viewings from the driver.
This restricted side vision is the result of the fact that the rear vision mirror, is just that, a mirror rather than a window to which one could look through.
The problem is particularly apparent in trucks and large pick up motor vehicles, where the rear vision mirror tends to be a long rectangular type construction extending or secured in a proximity not far from the front windscreen towards the side of the driver.
The problem becomes exaggerated when a truck is approaching an intersection and the driver needs to see whether or not vehicles coming from the side are approaching the intersection.
As experiences have shown, regrettably often the drivers vision is lost from this side viewing and therefore though there is a vehicle approaching the intersection from the right or left, they are lost behind that viewing section covered up by the rear vision mirror, with the driver only becoming aware of the presence of the vehicle, once the truck has entered the intersection, which regrettably is often too late with tragic circumstances occurring in a collision.
As the person skilled in the art would appreciate, the placing of the rear vision mirror on the right hand side and the driver being on the right hand side, is applicable to those countries that apply such a system of driving, the same problem would exist whether it is a left or right hand drive, and accordingly the rear vision mirror would be placed in that situation as well.
The purpose and the focus of this invention and the associated problem is to do with rear and side vision mirrors that are placed in vehicles, but then restrict vision of the driver within the vehicle.
Devices capable of switching between mirror like and transparent states have been known for many years. Such devices are commonly referred to in trade as “switchable mirrors” of which characterized by rare earth hydrids that were discovered and described by Huibertz et al, Nature L380,231 (1996), wherein the publication details are provided of a reversible metal to insulate a transition when a thin film (150 to 500 nm) of yttrium or lanthanum coated with a thin layer of palladium are exposed with hydrogen gas.
There is a transition whereby a metallic type hydride phase is converted to a semi conducting trihydride. This pioneering work led to the development of what was known as electro chromism whereby reversible change of colour exhibited by some materials when placed in an electric held could assist. In preparing switchable mirrors.
Certain kinds of material advantageously characterized by having a mirror like state when no electric field is present, are able to transfer to a transparent state when electric field is applied and vice versa using this kind of technology.
Thus, by placing films of electro chromatic material, such as those referred to by Huibertz and others since then, between electrodes, therein constructed will be an electro chromatic device, of which a person skilled in the art now commonly refers to as a “switching mirror” or “switching device”.
Nonetheless, there are problems with these switchable mirrors that have been developed using this electro chromism technology as well as those more recently developed switchable mirrors which are created by laminating glass particulate and applying a hydrogen source to the film which by placing the hydrogen to the particulate material is capable then of switching between a darkened colour and a transparent state.
This technology that hitherto has gone before for providing switchable mirrors based on these electro chromatic materials do have problems in their reversible conversion between the mirror and transparent state when exposed to outdoor environments.
Light exposure provided either by solar, street lights or the like in the outdoor environment, reflect on to the device limiting the effects of the darkened colour, such that light transmittance tends to pass through the device as well as reflecting back.
Accordingly, such switchable mirrors prepared using current electro chromatic materials though potentially highly reflective in an indoor environment, loose their highly reflective light capabilities as the mirror in an outdoor environment because of exposure in a lighted outdoor environment.
Attempts to overcome this reflective problem by altering the rare earth compounds or quantities of the electro chromatic materials have not proved advantageous, because if the laminated film provides too much of a coloured or darkened state, the properties then of the material do not permit the switch back of the device to a clear state when required.
Therefore, in the prior art of switchable mirrors between a mirror like and transparent state, though there is technology available, such technology is not yet suitable for outdoor use, and therefore used as rear vision mirrors.
There have been those in the prior art that have looked at this problem of the reduction of the darkening effect of glass when exposed to reflective light in an outdoor environment, but such interest has been associated with windows rather than mirrors.
Research Frontiers Inc of the United States have provided a variety of windows characterized by including a suspended particle device (SPD) light valve film, to which such film is suitable for use as a light modulating unit within a window.
Nonetheless, these light valves have also been known for many years, and as referred to by Research Frontiers Inc, a light valve is used to describe a cell formed of two walls that are spaced apart by a small distance, with at least one wall being transparent. The walls have electrodes thereon, usually in the form of transparent electrically conductive coatings. The cell contains a light modulating element, referred to as the activatable material, which may be either a liquid suspension of particles or a plastic film in which droplets of liquid suspension of particles are distributed.
The liquid suspension also known as liquid light valve suspension, or a light valve suspension comprises small particles suspended in a liquid suspending medium.
In the absence of an applied electrical field, the particles in the liquid suspension assume random positions due to what is known as “Brownian” movement. Therefore a beam of light passing into the cell is reflected, transmitted or absorbed, depending upon the cell structure, the nature of the concentration of the particles and the energy content of the light.
Thus as the person skilled in the art would appreciate the light valve is thus relatively dark in the off state, but when an electric field is applied through the liquid light valve suspension in the light valve, the particles become aligned and for many suspensions most of the light can pass through the cell, hence providing a transparent clear window.
Research Frontiers Inc in U.S. Pat. No. 6,936,193 go on to describe and claim for a film suitable for use as a light modulating unit of suspended particle device (SPD) light valve.
It is the intention of this invention to utilize such a feature, but nonetheless the feature itself of simply being able to tint a glass window between the darkened state where light is absorbed or reflected back to a state where light is permitted to pass through, does still not solve the problem to which this invention is directed to, that being a rear vision mirror which is switchable between two states, that being mirror like and a transparent state in an outdoor environment.
It is therefore an object of this invention to provide a switchable mirror that is adapted to be used as a rear vision mirror in a motor vehicle to improve road safety.
Further objects and advantages of the invention will become apparent from a complete reading of this description described herein.